Process for the refining of chromium ores



60. acid an Patented Oct. 27, 1931 UNITED STATES PATENT" orrlcs PA'O'LWEISE, 'WIESDOBF-ON-THE-RHINE, FRANZ SPEGHT,:OF OOLOGNE-ON-THE- RHINE,GERMANY, ASSIGNORS TO I. G. FABBEININDUSTBIE AKTIENGESELLSCHAFT, OFFBANKFORT-ON-THE-MAIN, GERMANY, A CORPORATION OF GERMANY PROCESS FOR THEBEFINING O F GHROMIUM OBES 80 Drawing. Application filed March 80, 1928,Serial No. 266,098, and in Germany April 18, 1927.

In the manufacture of chromium com-' pounds from chromium ores theimpurities, such as silicic acid, alumina, magnesia and the like,present. in the gangue, often give 15 rise to serious difficulties,since they not only consume anequivalent quantity of the material usedfor working up the ores, butalso render the ultimate roduct impure andcause difliculties in working because the solutions so cannot be readilyfiltered.

In accordance with the present invention the ore is-subjected-to theaction of alkalies in the absence of oxygen with the result that thegangue only is attacked, so that it will as be easily possible toseparate the ore almost completely from the gangue without loss ofchromium oxide occuring. By this sim le process inferior .ores can beconverted wit out great'expense into hi h so percentage ores, which isimportant not on y in the manufacture of chromium compounds, but also inconsiderably reducing the'cost of transport. Besides this, the oresubjected to this prelimina treatment [is very easily as worked up so tat higher yields can be .ob

tained.

As agents for partial working up alkali metal hydroxides and ea'rbonatesare suitable, employed either alonL-or in admixture with 10 one anotheror withsuch substances as lower the melting point. "The working up. can.

equally well be carried out either in the aqueous phase at temperaturesabove 100 C. with or without increased pressure, .Pyrogenis5 cally atthe melting point of. the o rative' agent used for working up the ore. eores thus treated, are quenched in water or in dilute alkali'solution,filtered land dried. 1 The workin%u agent and also the alumina, silicicj treating an ore under ike can be recovered from the filtrate in theknown manner. It is likewise possible by treating the filtered, stilldamp sludge with dilute acids to further enrich the ore in regard tochromium oxide.

. The following examples will illustrate our lnventionz Ema/mple1.-Finely ground chomium ore,

containing for example of Or o is mixed with the requisite quantity ofcaustic soda solution and heated in an autoclave in a nitrogenatmosphere to 200 C. with stirring. -When the working-up is complete,the oreis separated from the lye, washed with dilute. acid and dried.According to the source of the raw material, an ore is then ob-' tainedcontaining from -7 0% of Cr O Example 2.-Finely ground chromium ore ismixed with the just requisite quantit of a mixture of sodium carbonateand so ium hydroxide and heated ina rotating furnace in the absence ofoxygen to from 400-500" C.

The hot melt is quenched in water, the ore is separated .from the lyeand dried. .The lye is worked up to obtain sodium carbonate,

alumina and silicic acid, while the high percentage chromium ore, thusobtained, is further worked-up according to one of the customaryprocesses.

We claim: 1 In a process for the concentration of chromium ores, thestep which comprises treating an ore-at temperatures above 100 C. withan alkali in the absence of oxygen. I

2. In a process for the concentration: of chromium ores, the step whichcomprises treating an ore at temperatures above C.

with an alkali metal hydroxide in the absence of oxygen.

3. In a process for the concentration of. chromium ores, the-step whichcomprises. treating an ore at temperatures above 100 C. with an alkalimetal carbonate inthe absence of oxygen.

4. In a process for the concentration of ohromium ores, the 'step whichcomprises pressure at temperatures above 100 C. with an alkali in theabsenceof oxygen.

5. In a process for the concentration of chromium ores, the: step whichcomprises treating an ore under pressure at temperatures above 100 C.with an alkali metal hydroxide in the absence of oxygen.-

6. In a process for the concentration of 6 chromium ores, the step whichcomprises treating an ore under pressure at tempera tures above 100 C.with an alkali metal carbonate in the absence of oxygen.

In testimony whereof we have hereunto 10 set our hands.

PAUL WEISE. FRANZ SPECHT.

